18 ms·

I bought a CO2 monitor, and although the effects of CO2 in cognition and energy levels are debatable[1], it shocked me and raised awareness to how poor my indoo

I bought a CO2 monitor, and although the effects of CO2 in cognition and energy levels are debatable[1], it shocked me and raised awareness to how poor my indoor ventilation is. We live in a small apartment, and just being 30 min with 2 people in the room raises the CO2 ppm from 400 to >1000. Opening a window quickly lowers it. Never-mind doing some light activity like yoga or similar. So if we want to do something, I think the first step is really to get visibility to the problem, especially to the costs of the problem (productivity, public health, sick leaves, etc). [1] at the levels found in my apartment

rcme 3y ago
I think the first step would be to buy a second monitor, ideally from a different manufacturer, and verify that your readings are actually correct. My experience is that cheap monitors are basically random.
- lazide 3y ago
  At least one (Big Clive pulled it apart I think?) had an Ethanol sensor in it.
- bsder 3y ago
  Precisely this. I haven't seen anybody take any of the cheap CO2 sensors and demonstrate that they are anywhere in the range of the readings of a lab grade CO2 sensor.
- nicenewtemp84 3y ago
  If your reader raises it's reading as you sit in a small room, and lowers when you open a window... It's probably not at risk of being random. Inaccurate maybe, but still sensing in the correct direction.
mypastself 3y ago
Not to hijack your thread, but I wonder if anyone here’s built their own Raspberry/Arduino CO2 monitor? Which (reliable) sensors did you use? Did you find it more affordable than purchasing a monitor, especially if you already had unused microcontrollers lying around the house?
- Lukas_Skywalker 3y ago
  I built one based on the AirGradient DIY sensor [1]. It is open source, and you can order PCBs or build them yourself. It is also compatible with ESPHome. It uses the "Senseair S8" CO2 sensor, which costs a bit (25-30$), but (according to AirGradient) has a very high quality. [1]: https://www.airgradient.com/open-airgradient/instructions/diy-pro-v37/ https://www.airgradient.com/open-airgradient/instructions/di...
  - Rebelgecko 3y ago
    Seconding this recommendation. I was surprised how easy and cheap it was to order my own tweaked PCBs. Airgradient has also done a lot of testing to determine which components work well and what their different failure modes are. Depending on how many you build at a time, you can source all the parts for maybe $40-$60. Assembly is straightforward as long as you're comfortable with through-hole soldering (and if not, this is a great chance to learn). The design is also modular enough that it's easy to skip on things like the thermometer or particulate matter sensor if you're so inclined.
- deleted 3y ago
  [deleted]
- ProZsolt 3y ago
  I'm currently developing my own monitor based on Sensirion SCD40(CO2/temperature/humidity) and Plantower PMS7003(PM2.5). The SCD40 is lot smaller than any NDIR sensor, but with the same accuracy[1]. My goal is to get a cheap (~$50) sensor in a small package that I can put in every room in my house. It will be modular so I skip the display and the PM2.5 sensor and it can be cheap as ~$25 [1]: https://www.airgradient.com/open-airgradient/blog/co2-sensors-photo-acoustic-vs-ndir/ https://www.airgradient.com/open-airgradient/blog/co2-sensor...
- GloriousKoji 3y ago
  The microcontroller is the cheapest part! The good sensors that you want to use are in the $45 range. Look for "True" CO2 sensor that use some sort of optical technique to measure CO2. A lot of the really cheap CO2 monitors just measure VOC with some kind of metal element and approximate CO2. I like Sensirion SCD30 or SCD40.
isp 3y ago
> So if we want to do something, I think the first step is really to get visibility to the problem A sensible first step would be to very visibly display CO₂ monitors in buildings (e.g., throughout office buildings, schools, etc) Once the CO₂ levels become visible, this in itself creates an incentive to improve. Related from UK (2021): "All schools to receive carbon dioxide monitors" - https://www.gov.uk/government/news/all-schools-to-receive-carbon-dioxide-monitors https://www.gov.uk/government/news/all-schools-to-receive-ca...
- bsenftner 3y ago
  In Japan, it is common to see CO₂ monitor displays outside contained meeting spaces, such as theaters. My wife purchased an Aronet CO₂ monitor, and I took it with me on a business trip last week. The CO₂ while on the flight was in the 3000's range. The CO₂ at my client's office was in the mid 2000's range, as well as the hotel. Opening the hotel window the allowed 2 inches reduces CO₂ to the 600 range in 10 minutes, but the client's office windows do not open, and of course neither do the airplane windows. I've also noticed when working indoors or when driving, if the CO₂ is above 1500 I get drowsy, so the degree it is no longer responsible driving a car. Air safety: are we going to fight a moronic battle over this too?
  - giraffe_lady 3y ago
    No, there won't be any battle. If there were going to it would have been during covid, with improved indoor ventilation being one of the major components of an in-depth mitigation strategy. There was no meaningful attempt or debate about changing ventilation standards then when it would have tangibly saved lives, there certainly won't be now.
    - marcosdumay 3y ago
      The covid years were crazy. People kept cleaning everything with all kinds of poison (thank god somebody published early that alcohol at 70% is enough, otherwise I think we would see people dropping dead from too much poison), that was known to be useless by around April 2020, and yet everybody actively refused to talk about indoor ventilation. And most were the same people repeating the "are you for or against science?" line. Crazy years, dominated by completely random propaganda. Discussions on calmer times follow different rules, and if nobody decides to spend a lot of money stopping it, it can follow rational, evidence based lines.
c3534l 3y ago
> , it shocked me and raised awareness to how poor my indoor ventilation is. Do you want indoor circulation? Wouldn't that just mean your apartment loses heat/AC?
- swiftcoder 3y ago
  In a heating/cooling system that has been specifically designed to improve ventilation, one can pull fun tricks like using the outgoing (stale) air to help heat/cool the incoming (fresh) air. Also in some places houses are built with enough thermal mass that the air within the building doesn't contain the majority of the heat therein. In general there is likely some level of ventillation that will be worth taking on slightly increased heating/cooling costs.
- kevincox 3y ago
  You can use a heat exchanger to get "fresher" air while keeping the heat/cool inside. Although many places don't have this in place. It is probably mostly due to lack of awareness or concern than any technical reason.
  - endisneigh 3y ago
    Cost
    - switchbak 3y ago
      Letting your warm air go directly outside also has a cost. Getting poor air quality for decades also has a cost. Typing more than a one word reply is pretty cheap though.
      - endisneigh 3y ago
        you're right. things have tradeoffs. the point is that most barely have central AC with vents, let alone an HRV.
        3y ago
LeonM 3y ago
I don't understand why you are being downvoted, you raise a good point. Based on some HN comment from a while ago I invested in a CO2 meter (they are still quite expensive for some reason). And I share the same experience, CO2 levels can raise rapidly indoors, but simply turning on ventilation or opening a window very quickly lowers CO2 contents. Using the meter I found CO2 levels in my bedroom can become quite high at night. So I improved the ventilation in my bedroom, and in my case it helped me to achieve better sleep.
- ct0 3y ago
  I'm starting to think that having a better night's rest while sleeping in a tent is not from the ground you sleep on, but the fresh air you've had all night.
  - Cthulhu_ 3y ago
    It'll depend on the tent, I don't immediately associate tents with good ventilation.
    - gumby 3y ago
      A tent with poor ventilation rapidly becomes soggy.
  - prmoustache 3y ago
    you want to sleep below a tarp then, not in a tent.
  - kccqzy 3y ago
    My best sleep was on a camping trip when we decided that a tent wasn't necessary and we could just sleep outside watching the night sky. (This is of course highly location dependent. Now that I think about it, I was probably taking a bit more risk at that time than what I tolerate now.)
- anonyfox 3y ago
  … and people make joke about us Germans need to do „stosslüften“ (opening all windows in parallel to get fresh air in fast). also, are there really people that can (or even prefer!) to sleep with closed windows?! Only with AC blasting, right?
beebeepka 3y ago
If possible, I recommend ventilation by creating a current by opening the front door and cycling every room (windos, balcony doors) of your apartment. I do this every day regardless of the season. Works best during windy weather
- InCityDreams 3y ago
  *watch out for slamming doors and windows :-) Took me ages to work out how best to perform such in my place, and yes - daily opening, even for 5 minutes - does seem to help (me). I also do it last thing at night. In the morning - a less stuffy apartment. On work days, I'll probably open for a few minutes before going to work, but definitely after getting home.
  - oblak 3y ago
    I use mostly chairs and pillows to prevent doors from slamming. What challenges did you meet at your place?
sbaiddn 3y ago
That's why I'm not changing my very leaky and drafty windows - I don't want to live in a hermetically sealed Tupperware container. Once I install an HRV system then I'll do the windows!
- Abekkus 3y ago
  Or you could save $2k on materials & labor, and put in a filtered vent fan. You only need around 15CFM per resident. Household HRVs & ERVs have suspiciously low heat efficiencies for their costs.
  - BizarroLand 3y ago
    85-95% isn't suspiciously low. Where are you getting this information from?
  - sbaiddn 3y ago
    Does this "filtered vent fan" exchange air with the outside? If not, Im not interested.
  - symlinkk 3y ago
    Are you talking about a fan that simply blows outside air in? Wouldn’t that basically fight what the HVAC is doing? AFAIK the only real solution is an ERV / HRV, and they are extremely expensive (like $10k in my area)
    - balfirevic 3y ago
      No direct experience, but single-room HRV units look pretty cheap https://www.amazon.co.uk/single-room-heat-recovery-ventilation-system/s?k=single+room+heat+recovery+ventilation+system https://www.amazon.co.uk/single-room-heat-recovery-ventilati...
za3faran 3y ago
Which monitor manufacturer are you using?
- sergioisidoro 3y ago
  I bought mine from a construction material supply web store, and was looking for one of the cheaper ones. Its a Trotec. I wouldn't trust the absolute values so much, but i believe it's directionally correct.
Cthulhu_ 3y ago
It's a tradeoff, because good ventilation - ideally just open a window - also means heat is leaking out of the house, which costs money (and co2 emissions) to restore. There's cyclic systems, but I live in a neighbourhood where some houses were equipped with it; on the proper setting, it was too loud so people turned it down, then people got sick from high CO2 levels in their house.
- BizarroLand 3y ago
  There are ERV and HRV systems that will cycle fresh air in while exchanging the heat and moisture from the outgoing air to the incoming air. It's a neat technology but the jury is still out on it. Some people praise them, other people revile them, and they seem to be either too bulky or too cumbersome or too expensive or too inefficient for a DIY retrofit project.
clairity 3y ago
> "although the effects of CO2 in cognition and energy levels are debatable" it's really not debatable. the feeling of stuffiness is a function of many things, but environmentally, it's mostly temperature and humidity (we humans are hot and breathe out lots of humidity). there are no cognitive/energy effects until you get into the 10's of thousand of ppm, as the mechanism of action is competing out oxygen, not some intrinsic maladaption to CO₂, which is actually vital to life on earth. it's fashionable to hate on carbon right now (it's mediopolitical), and that's really all there is to it. particulates, VOCs and chemical off-gassing, on the other hand, do have known mechanisms of harm, and that's something you should be more concerned about, but not yet alarmed. most of that pollution comes from cars and coal/gas power generation, so long-term, we should move toward more efficient habitation (e.g., denser cities, public transit) and cleaner power generation (including nuclear) if we really care about our collective health. practically no one should be worried about CO₂ in their daily lives. it's thoroughly a red herring.
- sergioisidoro 3y ago
  Yes they are debatable. There are cognitive performance tests that show statistically significant decline in many tasks above 1500ppm, especially on planning tasks. That's independently of the feeling of "stuffiness". If these measurable declines have a sufficient impact on our lives and productivity is the debatable part. Edit: here's one reference: "We also found effects of CO2 (a proxy for ventilation) on cognitive function. For every 500ppm increase, we saw response times 1.4-1.8% slower, and 2.1-2.4% lower throughput" https://www.hsph.harvard.edu/healthybuildings/2021/09/09/impacts-of-indoor-air-quality-on-cognitive-function/ https://www.hsph.harvard.edu/healthybuildings/2021/09/09/imp...
  - clairity 3y ago
    if you look at the paper, you see no such conclusive evidence, but rather weak correlative assertions in noisy and complex environments. also notice the incentives and implicit bias of the involved. unbiased studies from the past several decades have so far shown cognitive effects require 10× that level of CO₂ to show any conclusive effects. even the pm2.5 effects attempt to make a short-term correlation, which is dubious at best. long-term pm2.5 effects are more conclusive, which is why we should be more concerned about them. CO₂ is a fashionable concern but not scientifically supported. more importantly, it distracts from things we really should be concerned about as states and nations, like actual pollution and the alarming concentration of power and wealth.
aidenn0 3y ago
I do wonder how much of it is CO2 levels themselves and how much of it is high CO2 being a proxy for poor ventilation.
kccqzy 3y ago
This is of course also the reason why I don't like most office buildings. They don't have operable windows and rely on centrally managed HVAC. They sometimes have CO2 sensors but the system is too opaque for occupants to figure out at which level the mechanical ventilation starts.

rcme 3y ago

I think the first step would be to buy a second monitor, ideally from a different manufacturer, and verify that your readings are actually correct. My experience is that cheap monitors are basically random.

lazide 3y ago
At least one (Big Clive pulled it apart I think?) had an Ethanol sensor in it.
bsder 3y ago
Precisely this. I haven't seen anybody take any of the cheap CO2 sensors and demonstrate that they are anywhere in the range of the readings of a lab grade CO2 sensor.
nicenewtemp84 3y ago
If your reader raises it's reading as you sit in a small room, and lowers when you open a window... It's probably not at risk of being random. Inaccurate maybe, but still sensing in the correct direction.

mypastself 3y ago

Not to hijack your thread, but I wonder if anyone here’s built their own Raspberry/Arduino CO2 monitor? Which (reliable) sensors did you use? Did you find it more affordable than purchasing a monitor, especially if you already had unused microcontrollers lying around the house?

Lukas_Skywalker 3y ago
I built one based on the AirGradient DIY sensor [1]. It is open source, and you can order PCBs or build them yourself. It is also compatible with ESPHome. It uses the "Senseair S8" CO2 sensor, which costs a bit (25-30$), but (according to AirGradient) has a very high quality. [1]: https://www.airgradient.com/open-airgradient/instructions/diy-pro-v37/ https://www.airgradient.com/open-airgradient/instructions/di...
- Rebelgecko 3y ago
  Seconding this recommendation. I was surprised how easy and cheap it was to order my own tweaked PCBs. Airgradient has also done a lot of testing to determine which components work well and what their different failure modes are. Depending on how many you build at a time, you can source all the parts for maybe $40-$60. Assembly is straightforward as long as you're comfortable with through-hole soldering (and if not, this is a great chance to learn). The design is also modular enough that it's easy to skip on things like the thermometer or particulate matter sensor if you're so inclined.
deleted 3y ago
[deleted]
ProZsolt 3y ago
I'm currently developing my own monitor based on Sensirion SCD40(CO2/temperature/humidity) and Plantower PMS7003(PM2.5). The SCD40 is lot smaller than any NDIR sensor, but with the same accuracy[1]. My goal is to get a cheap (~$50) sensor in a small package that I can put in every room in my house. It will be modular so I skip the display and the PM2.5 sensor and it can be cheap as ~$25 [1]: https://www.airgradient.com/open-airgradient/blog/co2-sensors-photo-acoustic-vs-ndir/ https://www.airgradient.com/open-airgradient/blog/co2-sensor...
GloriousKoji 3y ago
The microcontroller is the cheapest part! The good sensors that you want to use are in the $45 range. Look for "True" CO2 sensor that use some sort of optical technique to measure CO2. A lot of the really cheap CO2 monitors just measure VOC with some kind of metal element and approximate CO2. I like Sensirion SCD30 or SCD40.

isp 3y ago

> So if we want to do something, I think the first step is really to get visibility to the problem A sensible first step would be to very visibly display CO₂ monitors in buildings (e.g., throughout office buildings, schools, etc) Once the CO₂ levels become visible, this in itself creates an incentive to improve. Related from UK (2021): "All schools to receive carbon dioxide monitors" - https://www.gov.uk/government/news/all-schools-to-receive-carbon-dioxide-monitors https://www.gov.uk/government/news/all-schools-to-receive-ca...

bsenftner 3y ago
In Japan, it is common to see CO₂ monitor displays outside contained meeting spaces, such as theaters. My wife purchased an Aronet CO₂ monitor, and I took it with me on a business trip last week. The CO₂ while on the flight was in the 3000's range. The CO₂ at my client's office was in the mid 2000's range, as well as the hotel. Opening the hotel window the allowed 2 inches reduces CO₂ to the 600 range in 10 minutes, but the client's office windows do not open, and of course neither do the airplane windows. I've also noticed when working indoors or when driving, if the CO₂ is above 1500 I get drowsy, so the degree it is no longer responsible driving a car. Air safety: are we going to fight a moronic battle over this too?
- giraffe_lady 3y ago
  No, there won't be any battle. If there were going to it would have been during covid, with improved indoor ventilation being one of the major components of an in-depth mitigation strategy. There was no meaningful attempt or debate about changing ventilation standards then when it would have tangibly saved lives, there certainly won't be now.
  - marcosdumay 3y ago
    The covid years were crazy. People kept cleaning everything with all kinds of poison (thank god somebody published early that alcohol at 70% is enough, otherwise I think we would see people dropping dead from too much poison), that was known to be useless by around April 2020, and yet everybody actively refused to talk about indoor ventilation. And most were the same people repeating the "are you for or against science?" line. Crazy years, dominated by completely random propaganda. Discussions on calmer times follow different rules, and if nobody decides to spend a lot of money stopping it, it can follow rational, evidence based lines.

c3534l 3y ago

> , it shocked me and raised awareness to how poor my indoor ventilation is. Do you want indoor circulation? Wouldn't that just mean your apartment loses heat/AC?

swiftcoder 3y ago
In a heating/cooling system that has been specifically designed to improve ventilation, one can pull fun tricks like using the outgoing (stale) air to help heat/cool the incoming (fresh) air. Also in some places houses are built with enough thermal mass that the air within the building doesn't contain the majority of the heat therein. In general there is likely some level of ventillation that will be worth taking on slightly increased heating/cooling costs.
kevincox 3y ago
You can use a heat exchanger to get "fresher" air while keeping the heat/cool inside. Although many places don't have this in place. It is probably mostly due to lack of awareness or concern than any technical reason.
- endisneigh 3y ago
  Cost
  - switchbak 3y ago
    Letting your warm air go directly outside also has a cost. Getting poor air quality for decades also has a cost. Typing more than a one word reply is pretty cheap though.
    - endisneigh 3y ago
      you're right. things have tradeoffs. the point is that most barely have central AC with vents, let alone an HRV.
      - 3y ago

LeonM 3y ago

I don't understand why you are being downvoted, you raise a good point. Based on some HN comment from a while ago I invested in a CO2 meter (they are still quite expensive for some reason). And I share the same experience, CO2 levels can raise rapidly indoors, but simply turning on ventilation or opening a window very quickly lowers CO2 contents. Using the meter I found CO2 levels in my bedroom can become quite high at night. So I improved the ventilation in my bedroom, and in my case it helped me to achieve better sleep.

ct0 3y ago
I'm starting to think that having a better night's rest while sleeping in a tent is not from the ground you sleep on, but the fresh air you've had all night.
- Cthulhu_ 3y ago
  It'll depend on the tent, I don't immediately associate tents with good ventilation.
  - gumby 3y ago
    A tent with poor ventilation rapidly becomes soggy.
- prmoustache 3y ago
  you want to sleep below a tarp then, not in a tent.
- kccqzy 3y ago
  My best sleep was on a camping trip when we decided that a tent wasn't necessary and we could just sleep outside watching the night sky. (This is of course highly location dependent. Now that I think about it, I was probably taking a bit more risk at that time than what I tolerate now.)
anonyfox 3y ago
… and people make joke about us Germans need to do „stosslüften“ (opening all windows in parallel to get fresh air in fast). also, are there really people that can (or even prefer!) to sleep with closed windows?! Only with AC blasting, right?

beebeepka 3y ago

If possible, I recommend ventilation by creating a current by opening the front door and cycling every room (windos, balcony doors) of your apartment. I do this every day regardless of the season. Works best during windy weather

InCityDreams 3y ago
*watch out for slamming doors and windows :-) Took me ages to work out how best to perform such in my place, and yes - daily opening, even for 5 minutes - does seem to help (me). I also do it last thing at night. In the morning - a less stuffy apartment. On work days, I'll probably open for a few minutes before going to work, but definitely after getting home.
- oblak 3y ago
  I use mostly chairs and pillows to prevent doors from slamming. What challenges did you meet at your place?

sbaiddn 3y ago

That's why I'm not changing my very leaky and drafty windows - I don't want to live in a hermetically sealed Tupperware container. Once I install an HRV system then I'll do the windows!

Abekkus 3y ago
Or you could save $2k on materials & labor, and put in a filtered vent fan. You only need around 15CFM per resident. Household HRVs & ERVs have suspiciously low heat efficiencies for their costs.
- BizarroLand 3y ago
  85-95% isn't suspiciously low. Where are you getting this information from?
- sbaiddn 3y ago
  Does this "filtered vent fan" exchange air with the outside? If not, Im not interested.
- symlinkk 3y ago
  Are you talking about a fan that simply blows outside air in? Wouldn’t that basically fight what the HVAC is doing? AFAIK the only real solution is an ERV / HRV, and they are extremely expensive (like $10k in my area)
  - balfirevic 3y ago
    No direct experience, but single-room HRV units look pretty cheap https://www.amazon.co.uk/single-room-heat-recovery-ventilation-system/s?k=single+room+heat+recovery+ventilation+system https://www.amazon.co.uk/single-room-heat-recovery-ventilati...

za3faran 3y ago

Which monitor manufacturer are you using?

sergioisidoro 3y ago
I bought mine from a construction material supply web store, and was looking for one of the cheaper ones. Its a Trotec. I wouldn't trust the absolute values so much, but i believe it's directionally correct.

Cthulhu_ 3y ago

It's a tradeoff, because good ventilation - ideally just open a window - also means heat is leaking out of the house, which costs money (and co2 emissions) to restore. There's cyclic systems, but I live in a neighbourhood where some houses were equipped with it; on the proper setting, it was too loud so people turned it down, then people got sick from high CO2 levels in their house.

BizarroLand 3y ago
There are ERV and HRV systems that will cycle fresh air in while exchanging the heat and moisture from the outgoing air to the incoming air. It's a neat technology but the jury is still out on it. Some people praise them, other people revile them, and they seem to be either too bulky or too cumbersome or too expensive or too inefficient for a DIY retrofit project.

clairity 3y ago

> "although the effects of CO2 in cognition and energy levels are debatable" it's really not debatable. the feeling of stuffiness is a function of many things, but environmentally, it's mostly temperature and humidity (we humans are hot and breathe out lots of humidity). there are no cognitive/energy effects until you get into the 10's of thousand of ppm, as the mechanism of action is competing out oxygen, not some intrinsic maladaption to CO₂, which is actually vital to life on earth. it's fashionable to hate on carbon right now (it's mediopolitical), and that's really all there is to it. particulates, VOCs and chemical off-gassing, on the other hand, do have known mechanisms of harm, and that's something you should be more concerned about, but not yet alarmed. most of that pollution comes from cars and coal/gas power generation, so long-term, we should move toward more efficient habitation (e.g., denser cities, public transit) and cleaner power generation (including nuclear) if we really care about our collective health. practically no one should be worried about CO₂ in their daily lives. it's thoroughly a red herring.

sergioisidoro 3y ago
Yes they are debatable. There are cognitive performance tests that show statistically significant decline in many tasks above 1500ppm, especially on planning tasks. That's independently of the feeling of "stuffiness". If these measurable declines have a sufficient impact on our lives and productivity is the debatable part. Edit: here's one reference: "We also found effects of CO2 (a proxy for ventilation) on cognitive function. For every 500ppm increase, we saw response times 1.4-1.8% slower, and 2.1-2.4% lower throughput" https://www.hsph.harvard.edu/healthybuildings/2021/09/09/impacts-of-indoor-air-quality-on-cognitive-function/ https://www.hsph.harvard.edu/healthybuildings/2021/09/09/imp...
- clairity 3y ago
  if you look at the paper, you see no such conclusive evidence, but rather weak correlative assertions in noisy and complex environments. also notice the incentives and implicit bias of the involved. unbiased studies from the past several decades have so far shown cognitive effects require 10× that level of CO₂ to show any conclusive effects. even the pm2.5 effects attempt to make a short-term correlation, which is dubious at best. long-term pm2.5 effects are more conclusive, which is why we should be more concerned about them. CO₂ is a fashionable concern but not scientifically supported. more importantly, it distracts from things we really should be concerned about as states and nations, like actual pollution and the alarming concentration of power and wealth.

aidenn0 3y ago

I do wonder how much of it is CO2 levels themselves and how much of it is high CO2 being a proxy for poor ventilation.

kccqzy 3y ago

This is of course also the reason why I don't like most office buildings. They don't have operable windows and rely on centrally managed HVAC. They sometimes have CO2 sensors but the system is too opaque for occupants to figure out at which level the mechanical ventilation starts.